Method of coating articles with titanium and related metals and the article produced



May 27, .1969 R. F. KARLAK 3,446,543

METHOD OF COATING ARTICLES WITH TITANIUM AND RELATED METALS AND THEARTICLE PRODUCED Filed March 22, 1965 l4 ACTIVELY SINTERED TITANIUMLAYER TRANSITION nnmuu LAYER ALUMINA suasmu's Q FIG.2

' ACTIVELY smrenzo TITANIUM LAYER IB TRANSITION LAYER N's ALUMINASUBSTRATE INVENTOR. ROBERT F. KARLAK Agent United States Patent3,446,643 METHOD OF COATING ARTICLES WITH TI- TANIUM AND RELATED METALSAND THE ARTICLE PRODUCED Robert F. Karlak, Sunnyvale, Calif., assignorto Lockheed Aircraft Corporation, Burbank, Calif. Filed Mar. 22, 1965,Ser. No. 441,933 Int. Cl. C23c 3/04, 13/04; C03c 25/02 US. Cl. 117-22 7Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improvedmetal coating of titanium and related metals for articles, and moreparticularly, to an improved metal coating of titanium and relatedmetals for articles wherein the novel coating is applied to the surfaceof the article or portions thereof which are traditionally difficult toreach or in patterns of preselected design by use of an improved methodof coating the articles.

In the prior art it is well known that metals like titanium, zirconium,hafnium and uranium possess certain desirable properties which make themuseful for coating various surfaces of articles. It has been discoveredthat the use of such metal coatings, particularly titanium, on thesurface articles such as glass, quartz, beryllia, ceramic, porcelain,and the like, oifer several important advantages for both printed andintegrated electronic circuitry applications and for brazing and vacuumsealing techniques.

The present invention is particularly directed to the application oftitanium to an article for brazing and vacuum sealed techniques, but itis to be expressly understood that the invention may also be applicablefor other purposes such as printed and integrated electronic circuitry,for example, and encompasses the utilization of such metals aszirconium, hafnium and uranium as well as titanium. In the prior art,coating articles with titanium and related metals is specificallydisclosed in US. Patent Nos. 2,732,321, 2,996,401, and 3,022,201. Themethods disclosed in the cited patents involve applying a coating bymeans of 1) immersing the article to be coated in a fused inorganicmaterial bath of alkali metal halides or alkaline earth metal halideswhile holding a sheet of titanium in approximately the same surface areaas the surface of the article to be plated or with powdered titaniumpacked around the article to be plated, the article and the titaniumboth being immersed in the bath, thereby causing metallizing of thearticle with titanium; (2) applying a metallizing mixture to the articleto be coated by means of brushing, spraying, printing or otherwise,where the mixture consists essentially of a powdered manganese andtitanium with a powdered metal selected from the group consisting ofpowdered molybdenum or tungsten in a suitable binding agent such asnitrocellulose and heating to form a crystalline structure with thearticle to produce an interface zone which is chemical in nature ratherthan mechanical; and (3) applying a coating by means of a three-layersandwich assembly having an outer layer of titanium or titanium alloy,another outer layer of a ceramic substrate to be coated with titanium,and an inner layer sandwiched therebetween of a thin layer of saltcomprising any one of a mixture of the alkali or alkaline earth metalhalides which is heat-treated to thereby form a titanium thin-filmcoating on the surface of the article.

The foregoing processes have several undesirable features eithersingularly or in combination; namely, that the article can be coatedonly in the area where it is possible to place the titanium, titaniumpowder or titanium alloy in close proximity to the surface to be coatedon the article by some jigging means which in general is ratherdifiicult, impractical and uneconomical for mass production techniquesso that the processes are generally limited to fiat surfaces, or tothose surfaces which are readily amenable to a sandwich arrangement; orthat the titanium must be a part of the metallizing mixture and theresulting coating is not substantially a titanium one but a mixture ofthe metals and the oxides of the metals utilized in the metallizingmixture. Thus, the foregoing prior art methods are generally limited tometallizing those surfaces which are readily accessible and whoseconfigurations are regular and uniform. The salts utilized in several ofthe foregoing patents tend to drip or to run off of the surface beingcoated onto other portions of the article unless additional precautionsare taken to avoid this occurrence. In addition, such salts may beaccumulated on the apparatus of other auxiliary equipment being utilizedin the process, thereby causing other undesirable corrosive effects.Thus, it can readily be seen that it is highly desirable to provide aprocess that can easily and economically be controlled which eliminatesthe necessity for special jigging or fixtures or which is not limited toany configuration while substantially eliminating the possibility of anyrunoff of the salts or contamination of the equipment by theaccumulation of salts during the metallizing process.

In still another area of the prior art it has been found desirable toutilize divalent titanium which may be introduced into a fused salt bathin several ways. The most commonly used divalent compounds are titaniumdichloride, titanium di-iodide or titanium dibromide and the like, andthese divalent salts are pyrophoric and must be handled with extremecare to avoid possible harm to the workmen coating articles withtitanium. Thus it can be seen that the use of these compounds is highlyobjectionable since they create a hazard to the workmen.

The present invention obviates the foregoing and other disadvantages ofthe prior art by first providing a novel metallic surface coatingcomposition which has not been realized heretofore in the prior art,and, if realized, has not been heretofore recognized and utilized in themanner and for the purposes contemplated by the present invention. Inaddition, the present invention provides an improved method for coatingirregularly shaped bodies, both small and large surfaces, Whether solidor hollow, and in coating preselected areas by appropriate applicationtechniques when the improved coating mixture, of the present invention,is utilized. More particularly, the present invention provides for anovel metal coating composition and an appropriate process andmetallizing solution whereby metals such as titanium, zirconium,hafnium, and uranium may be applied to a surface of an article in amanner heretofore considered impossible, without the attendantcontamination associated with the prior art techniques. The presentinvention also provides the advantages of a technique and material whichmakes the metallizing process substantially more economical and easy toapply to both small and large sized bodies without the necessity of theattendant care required if pyrophoric materials are used, or withoutfear of shattering the article resulting from quick changes intemperature as when the article is dipped into a molten bath.Furthermore, the present invention provides a method vherein sharplydefined pattern edges are possible be- :ause of the particle size of themetallizing material utiized, and also provides a resulting coatingwhich adheres enaciously to the article being coated which is extremelytdvantageous for most applications.

Accordingly, it is a broad objective of the present inlention to providea novel metallic surface coating com- ;osition for brazing and vacuumsealing techniques or for 30th printed and integrated electronic circuitapplications.

It is another objective of the present invention to prolide an improvedmethod for coating articles with a novel metallic surface coatingcomposition of titanium, zirconium, hafnium and uranium and the like.

A more specific objective of the invention is to provide an improved andsimplified method for forming a novel metal coating composition oftitanium on an article of a preselected pattern and on preselectedportion of the body.

Another object of this invention is to provide a simplified andeconomical method for forming a thin uniform conductive film on flat,irregular, or curved surfaces of the body of a preselected pattern andon preselected area thereof which is readily adaptable forsemi-automatic or mass production techniques.

Still another object of this invention is to provide a metallizingsolution which may be utilized to readily deposit reproducible anduniform metal coating compositions on irregularly shaped bodies inintricate patterns which is more economical and practical thanheretofore known.

Concisely stated, the present invention provides a novel metal coatingcomposition for articles which is derived from utilizing a new andimproved method for coating articles in preselected areas or patterns onregular or irregular body configurations though the use of a uniquemetallizing coating which is adaptable for use with conventional sprayequipment and masking techniques and the like. More particularly, thenovel metal coating composition is derived from a unique metallizingsolution of the present invention which comprises a mixture of any oneor a mixture of the alkali or alkaline earth metal halides selected fromthe group consisting of sodium chloride, potassium chloride, calciumchloride, lithium chloride, and the like, and water in a saturatedsuspension solution, and powdered metal selected from the group oftitanium, hafnium, zirconium and uranium.

After the metallizing coating, which comprises the salts and metalparticles in a recrystallized form, has been applied to the article, thearticle is heat treated in a controlled atmosphere at a relative lowtemperature. The constituents of this coating material are in suchproportions as to eliminate traditional run-off and to assure readyadherence when applied in accordance with the teachings of the presentinvention or when subjected to the heat treatment step.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation andapplication, together with further objects and advantages thereof, willbe better understood from the following description thereof, in whichillustrative embodiments of the invention are disclosed by way ofexample. It is expressly understood, however, that the disclosedembodiments are for purposes of illustration and description only and donot define limitations of the invention.

FIGURES 1 and 2 are photomicrographs of sections through several ceramicsubstrates showing the thin transition film layer of titanium, bonded tothe ceramic substrates and the porous thicker layers of activelysintered titanium particles sintered to the thin transition layer.

Various and other objects and advantages will be apparent as the natureof this invention is more fully disclosed. More particularly, the aboveobjects are realized by a novel process which comprises c ating thesurface of articles such as ceramic, glass and the like, with ametallizing coating by means of spraying or painting or any suitablemanner of applying a metallizing solution comprising fine metallicsuspension in aqueous salt solution, and then heat-treating the coatedarticle in acontrolled atmosphere for a preselected time interval tothereby deposit the specific metal contained in the metallizing coatingon the surface of the article in a novel actively sintered manner toform a sintered agglomerate in a preselected pattern. In accordance withthe present invention in the preferred embodiment, the metallizingsolution comprises a mixture of finely divided metal particles, such astitanium, for example, having a U8. sieve number of 300 or greater, andpreferably greater than 325, any one or a mixture of the alkali andalkaline earth metal halide salts in preselected proportions and wateras the liquid vehicle. It should be understood at this point thatparticles that will pass through a mesh with a 325 US. sieve number,have a diameter less than 0.0017 inch.

In accordance with the teachings of the invention, an excellent metalcoating may be produced by utilizing a metallizing solution having byweight the following ranges:

Percent Titanium 1-50 Alkali metal halide salts 1-90 Alkaline earthmetals halide salts 1-20 Water, remainder to produce saturated solution.

The metallizing solution thus formed results in a saturated saltsolution in which is suspended the metal particles. The solution shouldbe thoroughly mixed so as to provide as uniform a distribution of thetitanium particles as possible throughout the liquid.

It should be noted at this point that in one embodiment of the inventionthe particle size of the metal constituent and the presence of calciumchloride are considered essential to the solution for successfuldeposition. The calcium chloride provides beneficial assistance inpromoting adhesion during the application of the saturated metallizingsuspension solution to the article and also enhances the rate ofdeposition to produce uniform metallizing coating of the article duringdeposition.

It has been found that when calcium chloride, which is hygroscopic, isomitted that the metallizing mixture does not adhere to the surface ofthe article to be coated during its application as well as when it ispresent. Thus, the calcium chloride contributes a moist phase to themetallizing mixture, which serves to make it more adherent to thesurface of the article during its application, and heat treating steps.As for the particle size of the metal, it has been found that if thesize is on the order of 250 US. sieve number the metallizing mixturewill not produce a coat of uniform thickness and, in addition, may beirregular and spotty in its coverage of the article. Such a coating isunsatisfactory as either a base material for over-plating with anothermetal for brazing or as an electrical conductor when the coating patternis employed as circuit wiring or as a base material for electricalcomponents on a substrate, such as capacitors and resistors.

Preparation of the articles to be coated may be commenced by thoroughlycleaning the article and then applying a uniform coating of themetallizing solution to the article by means of spray or paintingtechniques. The metallizing material preferably may be applied withsuitable spray equipment, such as a standard spray gun usable inspraying heavy duty paints. The pressure employed in applying suchmaterials is not critical, but should be of a magnitude such that themetal particles in the metallizing mixture are propelled with sufiicientforce to insure their adherence to the surface to be coated. It has.been found that air and the metallizer solution when sprayed in theratio of 1 volume solution 300 volumes air is satisfactory for thepresent process.

A more complete understanding of the present irrvention may be obtainedfrom the illustrative example. Very good success has been achieved byutilizing a metallizing solution consisting essentially by percent ofweight and by a more specific example by weight in grams of thefollowing proportions:

The metallizing mixture is produced by mixing together the dry saltspotassium chloride, sodium chloride, calcium chloride and titaniumparticles. The dry metallizing mixture is then mixed with the water toproduce a saturated metallizing solution with the metal particles insuspension. The solution must be thoroughly stirred prior to applicationand should be stirred continuously during the application step for bestresults, unless the metal particles are very fine, so as to staycontinuously in suspension.

In order to further enhance the deposition onto the surface of thearticle, it is preferable during the spray application step to move thearticle being coated or to move the spraying device so as toprogressively expose different surface portions of the article to thespray stream of the metallizing mixture. In this manner a more uniformcoat may be obtained. Although it is not critical for purposes of thisinvention, it is preferable as a rule to preheat the article beingcoated to a temperature of about ZOO-300 F. before applying themetallizing solution while maintaining the article at the elevatedtemperature if possible during the coating application the actualtemperature used is determined by the metallizer solution temperatureand that of the propelling air. Such preheating has been found tocontribute significantly to the adhesion of the metallizing coating.

After the coating step has been completed the article is next subjectedto a heat treatment step wherein the article is elevated to atemperature range of about 1200 F. to 1600 F. in a controlled atmospherefor a time period of about 5 to 120 minutes. Heating of the coatedarticle in a controlled atmosphere, such as argon, nitrogen, or forminggas, for examples, prevents oxidation of the deposited titanium. The useof such gases, as forming gas, is highly desirable because it is readilyavailable commercially at low cost.

During the heat treatment step it is believed that the alkali andalkaline earth metal halide salts go through a fluid state and therebycause a molecular transfer to the surface of the article from thetitanium particles to form a transition film layer bonded thereto, andthen the finely divided metal particles are actively sintered directlyover the transition layer. During the heat treatment step the meltedsalts occupy the interparticle volume and serve as the mass-transfermedium for activating the sintering of the particles. The article isthen slowly cooled to room temperature in the protective controlledatmosphere whereupon the remaining salts and metal particles which havenot reacted during the heating step are removed by rinsing in water.

The exact reaction or mechanism which occurs during the heat treatmentof the coated article cannot be stated with any absolute certainty. Theexact nature of the deposition is regarded as relatively unimportantsince the resulting coating has an electrically conducting coating onwhich other metals may be plated if such is desired, or may be used forpurposes of producing metal-toceramic or ceramic-to-ceramic bonds andthe like. Microscopic examination of sections cut from the treatedarticle, however, shows that the thin metallic film is an integral partof the article penetrating into the surface of the article, and that theactively-sintered agglomerate layer is bonded to this thin film layer.

With reference to FIGURES 1 and 2, respectively, there is shownphotomicrographs of sections through ceramic substrates 10 and 16 whichhave first thin transition film layers 12 and 18, and second porousmetallic layers 14 and 20 previously referred to as agglomerate layers.As shown in the figures, layers 12 and 18 are bonded to the surfaces ofthe ceramic articles 10 and 16 while the porous layers 14 and 20 are inturn bonded to layers 12 and 18. A closer analysis of the compositionformed under magnification of at least 250 times reveals that the thinlayers 12 and 18 are thin continuous layers having a relative density onthe order of to percent, while the porous layers 14 and 20 have arelative density on the order of 2050 percent.

As stated hereinabove, the exact nature of formation of the metalsurface coating composition is not exactly known or completelyunderstood; however, it has been theorized that the thin transition filmlayer is a result of molecular or ion transfer from the metal particlesactivated by the molten salts during the heat treatment step. It isbelieved that this process precedes or is concurrent with the formationof the porous, agglomerate layer which is bonded to the transitionlayer. Formation of the porous layer is theorized as resulting from theprocess known as activated sintering. However, the sintering process isone which depends upon the presence of the molten alkali or alkalineearth metal salts which act as an activator in the process. Thus, themetal particles are caused to be fused together in a porousconfiguration and are formed substantially simultaneously with the thintransition layer owing to the presence of the activator salts in themetallizing coating.

In the figures a substantially less dense layer is shown in FIGURE 1,layer 14, than that which is shown in FIGURE 2, layer 20. The thicknessof the porous layers 14 and 20 may be varied in several ways; namely, byvarying the quantity of metal particles in the metallizing solution orby varying the quantity of solution applied to the article prior to theheat treatment step.

With the resulting surface coating composition it has been found thatunder certain conditions brazing to another article with a suitablebrazing alloy may be accomplished by brazing directly to the resultantcoating. An excellent braze joint results having tensile strength asgood as, and in most instances better than heretofore obtained with theprior art coatings. More specifically in the prior art high strengthseals have been made employing metallizing composition of molybdenum andmanganese. The resulting coating is known to have and to be predicatedupon a glassy transition phase for its strength. In certain applicationsthe presence of the glassy transition phase is extremely objectionablebecause it introduces undesirable and poor thermal properties. Suchundesirable thermal properties have appeared when themolybdenum-manganese process is employed especially with beryllia. It iswell known that high purity beryllia has excellent thermal propertiesand is employed extensively for this reason. A typical high purityberyllia having excellent thermal properties is Thermalox 998 made byThe Brush Beryllium Company, Metal and Oxide Division of Elmore, Ohio.However, when the molybdenum-manganese process is modified so as toremove the glassy phase, and to restore its efiicient thermal propertiesthe bond strengths of the brazed joints of beryllia and other similarmaterials are too low to be usable. The present metal surfacecomposition is not predicated upon a glassy transition phase andconsequently, has excellent thermal properties when utilized withberyllia while providing bond strengths heretofore unknown in the priorart.

In addition to the excellent properties of mechanical strength forbrazing purposes and thermal conductive which the metal surfacecomposition of the present invention exhibits, the present inventionprovides a versatile and inexpensive process whereby the end product ofthe present invention may be produced. Furthermore, the resultingcoating may be utilized as a metallic layer which provides an excellentconductor for wiring patterns or may be employed as a base for a secondcoating which may be useful for a soldering or brazing surface, eitherwith or without a plating layer thereon, depending upon the application.

In the event that the thin conductive film deposited by the metallizingprocess in accordance with the present invention is to be used as awiring circuit pattern on an article, for example a ceramic circuitboard, there is no need to further process the film and it may be useddirectly for purposes of providing a conductive wiring or circuitpattern. In addition, it has been found that the conductive orelectrical characteristics of the metal deposited on an article aresimilar to the characteristics of the metal films deposited according tothe process disclosed in United States Patent No. 3,022,201 by Ross A.Quinn and Robert F. Karlak. Thus, it can be readily seen that the thinfilm obtained by mechanically removing a substantial portion of theagglomerate layer deposited in accordance with the present process maybe readily adaptable to microminiature electrical circuits whereinresistors and capacitor elements may be produced on a substrate by meansof anodizing in accordance with known technology in the prior art.

In closing it is useful to summarize some of the advantages of thepresent invention. One such advantage involves the use of water as asubstitute for an organic binder or vehicle which has been used in theprior art processes. In this connection, it should be noted that the useof such organic binders in combination with alkali or alkaline salts ingeneral create undesirable problems of a chemical nature. In particularthe interaction of organic compounds with the salts. In addition, theuse of organic binders is substantially more costly and critical thanthe use of water for mixing the solution and therefore causes themixture to be more costly.

Another advantage of the present invention arises from the fact that theingredients used in the metallizing solution in the prescribedproportion provide a solution which readily adheres to the surface ofthe article when applied thereto and thereby provides a uniform coatingthereon.

Yet another advantageous aspect of the present invention is that thetypes of materials used in the mixture disclosed by the presentinvention are much more economical than that employed in prior arttechniques. For example, the materials required for depositing singlelayer thin films on substrate as disclosed by U.S. Patent No. 3,022,201require the use of a thin sheet of titanium or titanium foil which issubstantially more costly than the titanium particles which are utilizedin the present invention. In addition, owing to the fact that thetitanium particles are extremely small and are placed directly on thesurface to be coated along with the salts associated therewith, there issubstantially greater and more efiicient coverage, on the order of tentimes as much, derived from the same quantity of salts which will beused in the process as disclosed in the aforementioned patent. Anotheradvantage results from the fact that the metallic film can be applied bythis process to any surface regardless of shape, contour, ororientation. Thus, it can readily be seen that the present process isone that is considerably more economical, practical, and versatile thanany process heretofore known.

Still another advantage of the present invention arises from the factthat the resulting metal coating has the properties of being useful forboth brazing or soldering ceramic to ceramic, ceramic to metal, or thelike especially when a suitable second plating coat is applied to theinitial metallizing coat, or as an electrical conductor for the wiringof circuit patterns or for microminiature electrical components such asresistors and capacitors when portions of the surface are anodizedaccording to techniques known heretofore in the prior art.

What is claimed is:

1. A process for forming a metal coating on the surface of an article ofglass, quartz, beryllia, ceramic or porcelain which comprises raisingthe article to an elevated temperature, applying a metallizing solutionto the surface of said article to form a metallizing coating thereon,said solution consisting essentially of at least one salt chosen fromthe group consisting of alkali metal halides and alkaline earth metalhalides, metal particles from the group consisting of titanium,zirconium, hafnium and uranium, and water, and then heating the articlewith said metallizing coating thereon to a predetermined temperature ina non-oxidizing atmosphere for a time sufficient to melt the salts inthe metallizing coating and to "cause sintering of the metal coatingconsisting essentially of a thin transition layer and a second porouslayer bonded to said first layer, the quantity of salts in themetallizing coating initially being suflicient to provide fluid boundarybetween the individual metal particles, and the metal particles and thesurface of the article to be coated when the salt melts.

2. The method of metallizing an article of glass, quartz, beryllia,ceramic or porcelain to provide a surface suitable for bonding to ametal, or metallized article to form between two articles a vacuum typejoint of high mechanical strength, which comprises coating said articlewith a metallizing coating from a metallizing solution consisting of onepercent to fifty percent by weight of titanium particles, one percent totwenty percent by weight of one or more of the alkaline earth metalhalides, one percent to ninety percent by weight of one or more of thealkali metal halides, and the remainder of water, and then firing thecoated article in a non-oxidizing atmosphere at a temperature at leastas high as the melting temperature of the alkali and alkaline halidesalts for a preselected period of time to cause sintering of the metalparticles.

3. A metallized ceramic article comprising a ceramic article, a firstthin metallic film transition layer bonded to the surface of saidceramic article, said film having a relative density of about topercent, a second metallic porous layer bonded to said transition layer,said second layer having a relative density of about 20 to 50 percentand comprising actively sintered metal particles of the same material assaid transition layer selected from the group essentially consisting oftitanium, hafnium, zirconium, and uranium, said first and second layersbeing formed substantially simultaneously from a metallizing coatingdeposited on said article essentially consisting of at least one saltselected from the group consisting of alkali metal halides and alkalineearth halides, metal particles selected from the group essentiallyconsisting of titanium, hafnium, zirconium, and uranium applied to saidarticle to a metal coat thereon which is bonded to said ceramic articleafter being heat treated.

4. A metallized ceramic article comprising a ceramic article and a firstthin-metallic film layer bonded to said ceramic article and a secondporous metallic layer bonded to said first layer, said first and secondlayers being of the same metal and selected from the group essentiallyconsisting of titanium, hafnium, zirconium, and uranium, said firstlayer at the surface of the ceramic article being in a form of acontinuous transitional layer having a relative density of about 90 to100 percent and said second layer being in the form of actively sinteredmetal particles having a relative density of about 20 to 50 percent.

5. A metallized article of glass, quartz, beryllia, ceramic or porcelaincomprising a first thin film transition layer bonded to the surface ofsaid article, said transition layer having a relative density of 90 to100 percent, and a second porous agglomerate layer bonded to saidtransition layer, said second layer having a relative density of about20 to 50 percent essentially consisting of actively sintered titaniumparticles derived from titanium having a particle size of at least 250U.S. sieve size.

6. A metallized article of glass, quartz, beryllia, ceramic or porcelaincomprising a first thin metallic film transition layer bonded to thesurface of said article, said film having a relative density of about 90to 100 percent, a second metallic porous layer bonded to said transitionlayer, said second layer having a relative density of about 20 to 50percent and comprising actively sintered metal particles of the samematerial as said transition layer, said first and second layers beingformed substantially simultaneously from a metallizing coating depositedon said article said metallizing coating being derived from a salt,essentially consisting of at least one salt selected from the groupconsisting of alkali metal and alkaline metal halides, metal particlesand water as a metallizing coating to said article and being bonded tosaid article by activated sintering as the coated article is heated.

7. The metallized article defined in claim 6 wherein said first andsecond layers are further defined as being selected from the groupessentially consisting of titanium, hafnium, zirconium and uranium.

References Cited UNITED STATES PATENTS 1,922,254 8/1933 McCulloch ll7l60X 2,732,321 1/1956 Gill et a1 117-131 2,746,888 5/1956 Ross 117123 X2,991,195 7/1961 Quinn l1716()X 2,996,401 8/1961 Welch et al. 117123 X3,022,201 2/1962 Quinn et a1 117221 FOREIGN PATENTS 104,564 7/1938Australia.

ALFRED L. LEAVI'IT, Primary Examiner. T. E. BOKAN, Assistant Examiner.

US. Cl. X.R. 65-32, 43, 59, 60; 1061, 38.27, 286; 1171l9, 123,

